What factor can lead to inaccurate HGN test results?

The accurate results of the Horizontal Gaze Nystagmus (HGN) test can be significantly influenced by both external environmental distractions and the health conditions of the subject.

Environmental distractions, such as noise, movement, or other interruptions in the vicinity during the test, can make it difficult for the subject to properly focus on the stimulus being presented. This can lead to misinterpretations of their eye movement, potentially resulting in false positives or negatives regarding impairment.

Health conditions of the subject, which may include neurological disorders, injuries, or certain medical conditions, can also affect the responsiveness of the eyes and the ability to perform the test accurately. For instance, a person with a vestibular disorder may experience nystagmus that is unrelated to substance impairment, which can skew the results of the test.

Together, these factors introduce variables that can compromise the validity of the HGN test, emphasizing the importance of controlled conditions and understanding the subject's health background when administering the test.